Quebrada de Ullum Dam, Dam in San Juan Province, Argentina

The Quebrada de Ullum Dam is a low embankment dam on the San Juan River in San Juan Province, Argentina. It forms a reservoir with an area of 32 square kilometers (12 square miles) and supplies water to a hydroelectric power station.

Construction of the dam began in 1969 and it was inaugurated on December 3, 1980. The Ullum II hydroelectric plant at its foot was added in 1988, and since then the dam has provided water for irrigation and power for the region.

The reservoir is a popular spot for locals and visitors, who come for water sports, camping, and picnics on the shores. Several beaches and clubs around the lake, such as Punta Tabasco and the San Juan Nautical Club, are well-known gathering places.

The dam is easily reached by car via Provincial Route 60, about 20 kilometers northwest of San Juan city. Visitors can drive along Provincial Route 14, which circles the lake and offers several spots to stop and take in the view.

The reservoir acts as a natural settling basin, allowing suspended material to sink so that cleaner water reaches the Marquesado treatment plant. This reduces the cost of filtering drinking water for the city of San Juan.